Builder Pattern

Builder pattern สำหรับสร้าง complex objects

Basic Builder

#[derive(Debug)]
struct Server {
    host: String,
    port: u16,
    max_connections: u32,
    timeout: u64,
    tls: bool,
}

#[derive(Default)]
struct ServerBuilder {
    host: Option<String>,
    port: Option<u16>,
    max_connections: Option<u32>,
    timeout: Option<u64>,
    tls: Option<bool>,
}

impl ServerBuilder {
    fn new() -> Self {
        Self::default()
    }

    fn host(mut self, host: &str) -> Self {
        self.host = Some(host.to_string());
        self
    }

    fn port(mut self, port: u16) -> Self {
        self.port = Some(port);
        self
    }

    fn max_connections(mut self, max: u32) -> Self {
        self.max_connections = Some(max);
        self
    }

    fn timeout(mut self, seconds: u64) -> Self {
        self.timeout = Some(seconds);
        self
    }

    fn tls(mut self, enabled: bool) -> Self {
        self.tls = Some(enabled);
        self
    }

    fn build(self) -> Result<Server, &'static str> {
        Ok(Server {
            host: self.host.ok_or("host is required")?,
            port: self.port.unwrap_or(8080),
            max_connections: self.max_connections.unwrap_or(100),
            timeout: self.timeout.unwrap_or(30),
            tls: self.tls.unwrap_or(false),
        })
    }
}

fn main() {
    let server = ServerBuilder::new()
        .host("localhost")
        .port(3000)
        .max_connections(500)
        .tls(true)
        .build()
        .unwrap();

    println!("{:#?}", server);
}